1. Field of the Invention
The present invention relates to a bonded compact and a method of producing a green bonded compact. Herein, the term “green” refers to a state before firing.
2. Description of the Related Art
There has been conventionally known a fired compact (ceramic bonded compact) produced by bonding, on each bonding surface of “a plate-like ceramic substrate having hole portions and being formed of a ceramic,” “a ceramic film having a thinner thickness than that of the ceramic substrate and being formed of a dense ceramic having a different composition or a different microstructure from that of the ceramic substrate.” Herein, the term “hole portion” refers to a through-hole or a recessed portion.
In regard to such a ceramic bonded compact, JP 2011-211033 A discloses, for example, “a method involving forming an electrode pattern and a blank pattern complementing the electrode pattern on a surface of a ceramic green sheet by a screen printing method or the like, followed by drying, to prepare the resultant ceramic green sheet in a plurality of numbers, and laminating the ceramic green sheets under heat and pressure.” Alternatively, JP 2011-211033 A discloses “a method involving forming an electrode pattern and a blank pattern complementing the electrode pattern on a carrier sheet by a screen printing method or the like, followed by drying, then transferring the resultant sheet on a ceramic green sheet via an adhesion layer to prepare the resultant ceramic green sheet in a plurality of numbers, and laminating the ceramic green sheets under heat and pressure.”
JP 10-242644 A discloses “a method involving applying thermocompression bonding to each ceramic green sheet on which a conductor circuit is transcribed,” and also discloses that the temperature at which the thermocompression bonding is applied is 80° C. or more and 150° C. or less and the pressure under which the thermocompression bonding is applied is 10 kgf/cm2 or more and 300 kgf/cm2 or less.
When any one of the above-mentioned methods disclosed in JP 2011-211033 A and JP 10-242644 A is appropriately used, the above-mentioned ceramic bonded compact is produced as described below. First, a ceramic green substrate, which is a precursor of a ceramic substrate (compact before firing), and ceramic green sheets, which are precursors of a ceramic film (compacts before firing), are prepared. Subsequently, a layer of a paste for bonding which contains a ceramic powder, a dispersion medium, and a binder is formed on the bonding surface of each of the ceramic green sheets. Then, while the state in which the paste layer is dry, and the bonding surface of each of the ceramic green sheets on which the paste layer is formed and the bonding surface of the ceramic green substrate are in contact with each other is kept, the ceramic green substrate and the ceramic green sheets are subjected to thermocompression bonding at a temperature of roughly 80° C. or more and 150° C. or less and a press pressure of roughly 10 kgf/cm2 or more and 300 kgf/cm2 or less. As a result, a green bonded compact (state before firing) formed of the ceramic green substrate and the ceramic green sheets is provided. This green bonded compact is fired, yielding the above-mentioned ceramic bonded compact.
By the way, the above-mentioned ceramic green substrate (compact before firing of a ceramic substrate) has hole portions, and hence the ceramic green substrate is liable to have deformation and cracking when an external force is applied. Owing to the fact, there has been a problem in that the ceramic green substrate is liable to have deformation and cracking when the above-mentioned thermocompression bonding is applied thereto.